Ride height adjustment system for a motorcycle

Abstract

An on-board mountable power unit, for ride-height adjustment of a “Softail” type of motorcycle, includes a pair of hydraulic actuators, each adapted to be mounted on the forward end of the rod of a piston and cylinder arrangement of a respective shock absorber of the rear suspension assembly of the motorcycle, after removal of the stub shaft extension of each rod. Each actuator is an hydraulic actuator ram having a housing, with longitudinally spaced forward and trailing ends between which is defined a chamber containing a piston movable between the ends. The piston has an elongate piston-rod that projects through an end plate at the trailing end of the housing, with a trailing end of he piston rod adapted for engagement with the forward end of the rod of the piston and cylinder arrangement of the respective shock absorber. The forward end of the housing has a forward extension, with a forward end of the extension engageable with the transverse bracket connecting the lower side members of the main frame of the motorcycle. Each actuator is able to connect the rod of the piston and cylinder arrangement of a respective shock absorber to the transverse bracket, similar to connection otherwise provided by the stub shaft extensions of the shock absorbers in the usual mounting arrangement for the rear shock absorbers of the motorcycle.

1 . An on-board mountable power unit for ride-height adjustment of a “Softail” type of motorcycle, wherein the unit includes a pair of hydraulic actuators, each adapted to be mounted on the forward end of the rod of a piston and cylinder arrangement of a respective shock absorber of the rear suspension assembly of the “Softail” type of motorcycle, after removal of the stub shaft extension of each rod; each of the actuators is an hydraulic actuator ram that has a housing with longitudinally spaced forward and trailing ends and that defines a chamber containing a piston movable between those ends and the piston has an elongate piston-rod that projects through an end plate at the trailing end of the housing and has a trailing end adapted for engagement with the forward end of the rod of the piston and cylinder arrangement of the respective shock absorber; wherein, at the forward end, the housing has a forward extension that has a forward end of the extension engageable with the transverse bracket connecting the lower side members of the main frame of the motorcycle; and wherein each actuator is able to connect the rod of the piston and cylinder arrangement of a respective shock absorber to the transverse bracket, with this connection similar to that otherwise provided by the stub shaft extensions of the shock absorbers in the usual mounting arrangement for the rear shock absorbers of a “Softail” type of motorcycle. 
     
     
         2 . The power unit of  claim 1 , wherein the housing of each actuator has a port through which pressurised hydraulic fluid can be charged to the chamber of the housing at a trailing side of the piston, whereby hydraulic fluid can be pumped into or from the chamber to drive the piston to or towards the leading or trailing end of the chamber to attain a desired position for the piston in the chamber so that, with the power unit installed on a “Softail” type of motorcycle, the rod of the piston of the piston and cylinder arrangement of the shock absorber of the motorcycle can be drawn to a required position to attain a required ride height. 
     
     
         3 . The power unit of  claim 1 , wherein the stroke of the piston of each of the actuators, for the typical stroke of the piston and cylinder of the shock absorber for a Harley Davidson “Softail” motorcycle, is at least 20 mm, preferably at least 21 mm, such as 22 mm, and the chamber of the housing in which the piston is movable has a diameter that is greater than the stroke of the piston, with a suitable diameter ranging up to about 45 mm, such as from about 38 mm to about 42 mm. 
     
     
         4 . The power unit of  claim 1 , wherein the axial length of the housing between the leading and trailing ends and the stroke of each piston within the housing are such that, with the actuators installed on a “Softail” type of motorcycle, the actuators are able to position the shock absorber at or between first and second extreme positions spaced by the stroke of the actuator pistons, by appropriate flow of hydraulic fluid to or from the chamber of each actuator to adjust the respective piston and, hence, 
     
     
         5 . The power unit of  claim 4 , wherein in the first of the extreme positions the adjuster plate at the leading end of the shock absorber housing is closely adjacent to the end plate at the trailing end of the housing of the actuator, while in the second position the adjuster plate and the end plate are axially spaced by substantially the stroke of the actuator pistons. 
     
     
         6 . The power unit of  claim 5 , wherein in the first position the leading end of the piston rod of each of the shock absorbers is received within the inner periphery of the end plate of the respective actuator housing, while the trailing end of the piston-rod of each actuator remains within the inner periphery of the adjuster plate of the respective shock absorber throughout positioning of the shock absorbers 
     
     
         7 . The power unit of  claim 1 . Wherein the forward extension of each actuator of the power unit of the invention is short relative to the removed stub shaft extension, due to space to be occupied by the actuator housing when the power unit is installed in a motorcycle grommet and a retaining nut threaded onto the stub shaft extension, with a first grommet provided on the forward extension of each actuator, against the outer surface of the leading end of the housing, with the forward extension then passing through the upright flange and being retained by a cup washer with a second grommet, and a retaining nut threaded onto the leading end of the forward extension. 
     
     
         8 . The power unit of  claim 1 , wherein in each of the actuators the piston-rod and the forward extension preferably are co-axial with each other and with the chamber in which the piston is movable, with the chamber of cylindrical form, with the piston-rod comprising an annular sleeve having a bore throughout the length of the sleeve and with the trailing end of the piston-rod internally screw threaded for engagement with the leading end of the rod of the shock absorber of the motorcycle. 
     
     
         9 . The power unit of  claim 8 , wherein each actuator includes a shaft that projects from the wall at the leading end of the housing, co-axially within the chamber and into the bore of the piston-rod sleeve, and the shaft, over a main part of its length, is a neat sliding fit in at least a leading end part of the bore of the piston-rod sleeve. 
     
     
         10 . The power unit of  claim 9 , wherein the shaft has a slightly larger trailing end part that is a neat sliding fit in a main part of the length of the bore of the piston-rod sleeve, such that at a rearward limit to the movement of the piston in the housing, a forwardly facing annular surface of the shaft within the sleeve bears against a rearward facing annular surface of the sleeve. 
     
     
         11 . The power unit of  claim 10 , wherein the forward extension also is annular sleeve having a bore extending throughout the length of the forward extension, and the shaft extends from within the bore of the forward extension in which it is retained, such as by screw-threaded engagement in the bore, with the shaft having a leading end that is at, adjacent to or close to the leading end of the forward extension, such as to be accessible from the leading end of the forward extension whereby the shaft is longitudinally adjustable in the forward extension to vary, by a limited amount, the extent to which the shaft extends into the chamber. 
     
     
         12 . The power unit of  claim 1 , wherein the forward extension and the housing of the actuator, including the end wall at the leading end comprise a single-piece, unitary construction produced by casting or machining of a suitable high strength metal, such as a high tensile steel. 
     
     
         13 . The power unit of  claim 1 , wherein the chamber is defined by the wall at the leading end of the housing, a peripheral wall of the housing and the annular end plate, with the end plate fitted at the trailing end of the housing and the piston-rod extending through the end plate, and wherein a relatively short trailing end section of the peripheral wall accommodates the end plate, the end section having a slightly larger internal diameter than the chamber along which the piston is movable, to provide an internal shoulder of the housing against which a peripheral flange of the end wall locates and a resilient “O” ring is forced against the trailing side of the peripheral flange by a retaining circlip to provide a static seal between the housing and the periphery of the end wall. 
     
     
         14 . The power unit of  claim 13 , wherein the respective port through which pressurised hydraulic fluid can be charged to the housing of each actuator communicates with an annular groove formed around the inner surface of the trailing end section of the housing on the leading side of the dynamic seal provided against the flange of the end plate, with the hydraulic fluid able to pass to the chamber via a number of radial grooves in the internal shoulder of the housing or in an outer margin of the leading face of the end plate. 
     
     
         15 . The power unit of  claim 1 , further including an hydraulic power unit operable to supply pressurised hydraulic fluid to, or to enable hydraulic fluid to discharge from, the chamber of each actuator to enable adjustment of the ride height of a “Softail” type of motorcycle on which the power unit is mounted. 
     
     
         16 . The power of  claim 15 , wherein the hydraulic unit includes a reservoir containing a sufficient volume of hydraulic fluid, a pump for supplying hydraulic fluid from the reservoir to the chamber of each actuator via a respective hydraulic fluid flow line and enabling a return flow of fluid to the reservoir, and an electric motor operable for driving the pump. 
     
     
         17 . The power unit of  claim 16 , further including ancillary circuitry connectable to the electric system of the motorcycle for operating and controlling the electric motor according to the requirements of the motorcycle rider. 
     
     
         18 . The power unit of  claim 16 , wherein the reservoir, pump, hydraulic fluid flow line and electric motor of the power unit are assembled into a compact unit able to be installed and secured between the lower side members of the main frame, adjacent to the leading side of the transverse bracket that connects those side members, with the hydraulic unit housed in a frame structure mountable in relation to the lower side members of the main frame. 
     
     
         19 . The power unit of  claim 18 , wherein the hydraulic unit is secured by being housed in a frame structure having an under-tray assembly, designed to be positioned under the lower side members of the main frame, and a mounting bracket assembly able to be located between those side members and secured to the under-tray assembly. 
     
     
         20 . The power unit of  claim 19 , wherein the bracket assembly consists of a leading mounting bracket and a trailing mounting bracket each of which can be connected to the under-tray such as by screw-threaded bolts, with the trailing mounting bracket shaped to fit against the leading surface of the transverse bracket that connects between those lower side members, with each end of the trailing bracket shaped to fit around the retaining nut threaded onto the leading end of the forward extension of each actuator, and the trailing bracket adapted to be held in such position by having hooks that engage over the upper edge of the upright flange of the transverse bracket, and the leading mounting bracket is spaced forwardly from the trailing mounting bracket and held by having respective end portions each engageable around a respective lower side member. 
     
     
         21 . The power unit of  claim 15 , wherein the electric motor is a 12 volt DC motor, operable on a supply current of about 10 amps, and the pump comprises a bi-directional, gear type of pressure pump provided with a pressure relief valve. 
     
     
         22 . The power unit of  claim 15 , wherein the reservoir defines a chamber in direct communication with an intake port of the pump and is in the form of a resilient, synthetic rubber housing having a mouth bordered by a peripheral out-turned flange by which the housing can be clamped against a mounting block in relation to which the motor and pump also are secured. 
     
     
         23 . The power unit of  claim 1 , further including a modified adjuster plate for each shock absorber, to replace the original equipment adjuster plate, and adapted to be used in combination with an internal collar device that is adapted to be fitted around the leading end of the cylinder of the piston and cylinder arrangement of the shock absorber; and wherein the collar device has inner and outer concentric parts that are coupled together by a screw-threaded engagement so that, with the inner part axially fixed on the cylinder, the outer part is able to rotate and move axially relative to the inner part. 
     
     
         24 . The power unit of  claim 23 , wherein the inner part is adapted to be releasably fixed on the cylinder by the inner part having a bore through which the cylinder is received, with the bore tapered so as to as to have a slightly frusto-conical form, with half angle of about 1 or 2 degrees, that increases slightly in diameter towards the leading end, whereby the inner part can be fixed on the cylinder by being forced axially over a wire snap ring located in a peripheral groove in the outer surface of the cylinder so the tapered bore surface bears against and compresses the snap ring into the groove 
     
     
         25 . The power unit of  claim 23 , wherein the collar device enables variation in the degree of pre-load applied to the spring of the shock absorber, with the pre-load varied by rotation and axial adjustment of the outer part of the collar device relative to the inner part. 
     
     
         26 . The power unit of  claim 25 , wherein rotation of the outer part of the collar device is able to be achieved by inserting the of prongs of a suitable tool through selected openings spaced around the outer periphery of the modified adjuster plate, and engaging the prongs with formations of the outer part of the collar device. 
     
     
         27 . The power unit of  claim 26 , wherein the modified adjuster plate has at least three uniformly spaced openings through at least two selected openings respective prongs are able to be inserted to enable the tool to apply required torque for rotating the modified adjuster plate and the outer part of the collar device, with the outer part having a circumferential array of longitudinally extending openings or keyways in selected ones of which the prongs are locatable for rotation of the outer part by the tool. 
     
     
         28 . The power unit of  claim 27 , wherein the openings or keyways are defined by the outer periphery of the outer part being defined by a circumferential array of alternating ribs and grooves, with the grooves being U-shaped in cross-section.